Teeth are designed to chomp down on food and are not supposed to touch the top of each other when you're biting down or closing your mouth.
Still teeth do touch each other when you chew or close your mouth but the teeth are designed to overlap each other and not sit directly on top of each other.
If your teeth close down on top of each other then your teeth must be misaligned but if the teeth are overlapping each other when the teeth are chewing or your mouth is closed then the teeth are aligned correctly.
So yes teeth can and do touch each other but they overlap when they touch.